For magnetic resonance imaging it is important that a patient does not make any movements for the entire duration of the magnetic resonance examination, in particular in a region of the patient which is relevant to the magnetic resonance examination. Movements by the patient during the magnetic resonance examination can produce artifacts in the magnetic resonance images, which can then lead to an erroneous interpretation during a medical evaluation of the magnetic resonance images, and/or to a reduction in their interpretation value. It may, moreover, be necessary for the magnetic resonance examination to be repeated. Particularly with magnetic resonance examinations of patients inclined to claustrophobia and/or patients suffering from pain and/or children, it is often difficult for the patient to remain lying motionless for the duration of the magnetic resonance examination.
Methods are already known with which a movement of the body of the patient can be acquired by means of the magnetic resonance examination, and subsequently a change is made in the course of a measurement sequence, such as, for example, an adjustment of a gradient plane. Such methods, however, must be developed individually for each magnetic resonance sequence.
It is further known to acquire the movement of the patient by means of a sensor unit. Thus, for example, from U.S. Pat. No. 8,121,361 B2 an apparatus is known for the acquisition of a movement by a patient, with which marking elements, in particular optical marking elements, are arranged on the patient. A position of these marking elements is acquired by means of a detection unit, and from this a change in position and/or a movement of the patient is identified. In this situation, however, before the magnetic resonance examination, the patient must be prepared for such a measurement by medical service personnel, which leads to a time-consuming preparation phase for the magnetic resonance examination.
An apparatus is also known from U.S. Pat. No. 7,945,304 B2 with which, by means of an ultrasound unit, organs of the patient are measured, wherein for this purpose a detector unit must rest directly against the tissue of the patient. Such a measurement, however, is difficult to carry out due to the restricted amount of space available, since in most cases for a magnetic resonance examination a local magnetic resonance coil rests directly against and/or at a short distance from the region of the patient which is to be examined.